Degumming silk



Patented Oct. 27, 1931 UITED STATES PATENT OFFICE NORMAN D. HARVEY, J'ROF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO CARBIDE & CARBON CHEMICALSCORPORATION, A CORPORATION OF NEW YORK DEGUMMING SILK No Drawing.Application filed February means of alkaline solutions, soap solutionsor even boiling water.

The usual degumming process is to boil the silk, in skein form or afterweaving, in a 7 water solution of a sodium or potassium soap. To removethe gum effectively the soap solution should have a pH of about 10.0.More strongly alkaline solutions damage the fibre rather rapidly, andeven where the pH is below 10, prolonged boiling will injure the silk.It is customary to use high-grade olive oil soaps which are as nearlyneutral as pos sible. A solution containing about 1% of soap isoftenused, the weight of soap being about of the weight of silk-to bedegummed. During the degumming operation, the pH of the soap solutionfalls slowly to a value of about 8.5 to 9.0, at which itremainspracticallystationary. This change in the solution is explainedby. the acidic properties of the gum dissolved. As its pH drops, thesoap solution becomes less and less efiective as a degumming agent.

Ihave found that monoethanolamine, more or less completely saponifiedwith oleic or other fatty acid, is an" excellent silk degumming agent.Monoethanolamine,

(OHQOHCHZNHQ),

is a high boiling, hygroscopic, slightly yellow liquid of faintammoniacal'odor having an alkaline reaction and a pH of about 11.6. Silkdegummed with this reagent is somewhat whiter and softer than silkdegummed with the best olive oil soaps, and the material has otheradvantages as a degumming agent which will appear below.

I prefer to use a mixture of monoethanolamine and fatty; acid containinga stoichiometrical excess of the amine, for example, con" taining aboutequal weights of the amine and the fatty acid. The presence of the fattyacid lowers the pH of the mixture to about 10.0,

and this .value is found to remainalmost 3, 1930. Serial No. 425,727.

constant until a considerable proportion of sericin has been dissolvedin the solution, owin to the fact that the original mixture containsconsiderably more base than is required for a neutral soap. In otherwords, monoethanolamine gives adegumming reagent whichretains itsefliciency longer than the soaps used heretofore.

Comparing freshly made solutions, monoethanolamine soaps are somewhatmore efficacious than -olive oil soap. A solution containing 0.4 gram ofmonoethanolamine and- 04 gram of oleic acid in 99.2 grams of waterdegums silk at as high a rate as a 1% s'plu tion of olive oil soap. Themonoethanolamine oleate prepared with'an excess of base, as describedherein, may be'rinsed from the silk somewhat more readily thanalkali-metal soaps.

Less accurate control of the saponification' process is required whenmonoethanolamine is used as the base. The pH of this compound, I

being low as compared with caustic alkalies,

an excess of base is much less likely to raise the pH of the gumm'ingsolution to a value sufiiciently high to injure the silk.

Instead of oleic acid, other soap-forming fatty acids may be used, theproportions of amine and fatty acid being adjusted to give a suitablepH. y

i I claim: v

1. Process of degumming silk which comprises dissolving the sericin in asolution containing a monoethanolamine soap, and an excess of the amine.

2. Process of degumming silk which comprises dissolving the sericin in asolution containing a monoethanolamine oleate, and an excess ofmonoethanolamine.

3. Process of degumming silk which comprises dissolving the sericin in asolution containing equal weights of monoethanolamine and oleic acid;

In testimony whereof, I aflix' my signature.

' NORMAN D. HARVEY, JR.

